Body charge indicator for trackless trolley coaches



July 26, 1938.

L. C. JOSEPHS, JR, ET AL BODY CHARGE INDICATOR FOR TRACKLESS TROLLEY COACHES Filed Jan. 25, 1936 Lealiageliewlauce I INVENTORS L z /m (g1; 67 Jaaqp/w; Jr:

9 andiamrzzrme Jfiuhe,

BY W

Patented July 26, 1938 BODY CHARGE INDICATOR FOR TRACKLESS TROLLEY COACHES Lyman O. Josepha, Jr.

J; Heine, Bethlehem, Pa.,

, Allentown,

and Lawrence assignors to Mack Manufacturing Corporation, a corporation 01' Delaware Application January 23, 1936, Serial No. 60,434

The present invention 5 Claims.

relates to signal devices for trackless trolley coaches and the like, by means of which indication is given of the existence of a charged condition of the coach body.

Inasmuch as trackless trolley coaches and the like run on rubber tires which insulate the metallic parts thereof eiiectively from the ground,

the body frequently is in a charged condition where a difference of potential exists between the body and the ground. This condition is parto arise due to leakage through raulty insulation and obviously is an extremely undesirable one inasmuch as it endangers incoming and outgoing passengers.

An object of the present invention, accordingly,

is to ,crovide a device by means of which the existence or indicated.

a charge in the vehicle body may be it further object of the invention is to provide a mechanism by means of which eifective indica- Further objects of the invention will appear as it is described in detail in connection with the accompanying drawing, wherein the single flg ent invention, including the electrical circuits by means of which the Referring to the above device is operated.

drawing, the power circuit from which the vehicle operating mechanism is supplied with power is indicated at I and 2, I being the This circuit negative wire and 2 the posimay receive power from a power line through trolley mechanism which need not be described herein. At 3 there is shown a Thyratron tube, connected to wires 5 and 6, across the wires l and 2 switch mechanism l. The controlled by a coil 8 the wires I and 2 and contacts 9, IO, N and the filament 4 01 which is which are connected through a polarized polarized switch i is which is connectedacross is provided with stationary i2. Contacts 9 and i2 are connected to wire 2 through a wire l3, while contacts i and ii are connected to wire I through a wire M. The movable contacts polarized relay 1 is provided with I5 and I6, contact I5 being movable between the stationary contacts 9 and I0, while contact I 6 is movable between ary contacts H and I2.

station- Movable contact i5 is connected to the wire 6 by means of a wire i1, while is connected to wire I. A

movable contact i6 current limiting reslstor i8 is connected in the circuit including wire 8 in order to properly adjust the potential across the filament 4.

The plate l9 of the tube 3 is connected to an indicator 20 by means of a wire 2|, the indicator being connected to wire ll through a resistor 22.

The grid 23 of the tube 3 is connected to a battery 24 by means of a wire 25, the other terminal of the battery being connected to the frame 2B of the vehicle by means of a wire 2?. It should be noted that the battery 24 is so connected that the negative terminal thereof is connected to the grid 23 while the positive terminal is connected to the frame 26.

In the drawing the resistance 28 represents the leakage resistance between the positive cirance being due to the insulation resistance of fixtures and various other parts. The negative trolley wire i is grounded at 29. It will thus be seen that passengers will contact both the frame and the ground at the same time. If the leakage resistance 28 is sumciently high, there will be very little voltage between the ground 29 and the frame 26. If, on the other hand, this leakage resistance is very low, the passenger may get a veryserious shock. Inasmuch as the voltage across the leakage resistance 28 is impressed on the grid 23 of the tube 3 which is connected to the frame 26 through battery 26, this voltage serves to overcome the bias voltage of the battery 24 and allows the tube to break down, cause ing a current flow through the indicator circuit iii, if the leakage resistance falls below a predetermined amount. In this fashion, the characteristics of battery 24 determine the point at which the tube breaks down and a signal is given.

The battery 24 is of such character that if the potential between the frame and the negative trolley exceeds a It will be seen that the polarized relay 1 preserves the proper polarities on the plate and filament of the tube 3 in the event that the overhead polarities are reversed inasmuch as the eliminating a relay.

Inasmuch as a relay or meter would furnish a direct connection between the coach frame and the main power circuit, the very condition which is sought to be avoided would be produced, whereas, by means of the tube and circuits described above, no direct connection exists between the power circuit and the frame.

While the invention has been described with specific reference to the circuit and mechanism shown in the accompanying drawing, it is not to be limited, save as defined in the appended claims.

,We claim:

1. A device tor indicating a charged condition of the frame of a vehicle having a power circuit comprising an indicator, an electronic tube having a filament, a plate and a grid, a polarized relay connected across the power circuit and having a plurality of contacts, circuits to connect the contacts to the filament of the tube and the power circuits, a circuit to connect the indicator to the plate of the tube and one of the contacts, a circult to connect the grid of the tube to the frame of the vehicle, and a battery in the last named circuit. a p

2. A device for indicating a charged condition of the frame of a vehicle having a power circuit comprising an indicator, an electronic tube having a filament, a plate and a grid, a polarized relay connected across the power circuit and having a plurality of contacts, circuits to connect the contacts to the filament of the tube and the power circuits, a circuit to connect the indicator to theplate of the tube and one of the contacts to connect the plate to the positive side of the power circuit, a circuit to connect the grid of the tube to the'fframe of the vehicle, and a battery in the last named circuit with the positive terminal thereof connected to the frame of the vehicle.

3. Adevice for indicating a charged condition oi the heme of a vehicle having a power circuit comprising an indicator, an electronic tube having a filament, a plate and a grid, circuits to connect the electronic tube to the indicator and vehicle power circuit, means to bias the grid of the tube to render the indicator inoperative, and means to connect the tube to the irame to cause a difierence of potential existing between the frame and the grounded side of the power circuit to oppose the grid bias and actuate the indicator.

4. A device for indicating a charged condition of the frame of a vehicle having a power circuit comprising an indicator, an electronic tube having a filament, a plate and a grid, circuits to connect the electronic tube to the indicator and vehicle power circuit, a polarized relay connected in the circuit including the electronic tube and vehicle power circuit, a circuit to connect the grid of the tubeto the frame, and means in the last named circuit to bias the grid whereby a difference of potential existing between the frame and the grounded side of the power circuit tends to overcome the bias and to actuate the indicator.

5. A device for indicating a charged condition of the frame of a vehicle having a power circuit comprising an indicator, an electronic tube having a filament, a plate and a grid, circuits to connect the filament and plate of the tube to the vehicle power circuit, means to bias the grid of the tube to render the indicator inoperative, the indicator being in the circuit of the plate of the tube, and means to connect the grid of the tube to the frame through a battery to cause a difierence of potential existing between the frame and the grounded side of the power circuit to oppose the grid bias and actuate the indicator.

LYMAN C. JOSEPHS, JR. LAWRENCE J. HEINE. 

